Window balance

I need to replace two balances marked "26 4 FL CALDWELL". They are from a double pane non-tilt window with a 1/2" channel that measures 27" (just the metal channel). The sash weighs between 19 and 21 pounds (my scale fluctuates). I cannot determine if my top and shoe matches the S380, S385, or S395 series. The top seems to be a 19-005, but I have no clue on the shoe. Your advice is greatly appreciated.